Fixed focus head lamp



Oct; 13, 1931. s. F. ARBUCKLE 1,826,712

FIXED FOCUS HEAD LAMP Filed July 7, 1927 5 Sheets-Sheet 1 ATTORNEY s. F. ARBU CKLE FIXED FOCUS HEAD LAMP Filed July '7, 1927 5 Sheets-Sheet 2 mmim m mmw 1 INVENTOR 5/1/7054 f ARBUC/(L mmmmmmmmmm n I ATTORNEY 1931- s. F. ARBUCKLE.

FIXED FOCUS HEAD LAMP Filed July '7, 1927 5 Sheets-Sheet 3 INVENTOR .SAm/EL f7 flkauc/as r '7 f ,I

ATTORNEY Oct. 13, 1931. s. F. ARBUCKLE' FIXED FGCUS HEAD LAMP 5 Shee ts-Sheet 4 Filed July 7, 1927 INVENTOR 534/1054 f A2500:

I ATTORNEY Oct. 13, 1931. s. F. ARBUCKLE FIXED FOCUS HEAD LAMP Filed July 7, 1927 5 Sheets-Sheet 5 INVENTOR 54/1054 FAR uC/mE ATTORNEY Patented (lot. 13, 1931 UNITED STATES PATENT sAMUEL I. ARBUGKLE, or HIGHLAND PARK, MICHIGAN, ASSIGNOR To MonoqaAmLmi-sx CORPORATION, or DETROIT, M oHIoAN, A CORPORATION OF DELAWAR 1: I

FIXED FOCUS HEAD, LAMP Application filed July 7,

' automobiles and especially that type of headdriving in traflic or parking.

light adapted to use a light bulb having two filaments in order to project two separate beams, one for fast driving, and the other f0 Headlights are' commonly in use in which a two filament bulb is mounted in a parabolic reflector, and an adjustment is provided whereby it may be moved both axially and vertically so that the filaments may be placed in exactly the proper position with respect to the focal point of the reflector so that the desired beams may be produced. This adjustment was found to be necessary because of the slight movement almost always found between the bulb and the socket, because of the tolerance in the manufacture of the electric light bulbs wherein the spacing of the filaments with respect to the envelope of the bulb varies slightly, in some instances about 3/64 of an inch and because reflectors were used having a short focal length which made them very sensitive to variations of the light source. Hence, when a new bulb was inserted in a headlight, the filaments mi ht be entirely out of place with respect to t e reflector and necessarily bad to be'adjusted to obtain the proper result from the headlight. This adjustment of the bulb in the headlight has been found objecionable because of the fact that it is a matter of some nioety to get the filaments in their proper position, whlch is not easily accomplished by the average man, with the result that many of theheadights now in use while provided with adjustng means are very much out of focus due to mproper adjustment and resulting in glaring lights which are dangerous and exceedingly annoying to other drivers, when the cars to which they are attached are driven on the highways.

It is-one of the objects of this invention,

therefore, to provide a-lieadlight inwhich the necessity for a focusing ad ustment is absolutely eliminated and in which a stand ard bulb may be inserted with the assurance in spite of manufacturing tolerances that its filamentwill be properly=focused.-

l In driving at night-it is very desirable to 192?. Serial No. 203,948.

have a driving beam with the intensity at the.

-top thereof, and this has been accomplished where a two filament bulb has been used in a short focal length reflector by displacing the lower filament below the axis of the reflector, which throws theintense part of the beam or that part reflected by the portion of the reflector which lies behind the focal plane, upwardly, so that the beam has considerable intensity at the top and shades down to a dimmed 'light at the bottom. Such axconstruction has been illustrated in my Patent 1,662,938, dated March 29, 1927. If the focal length of the reflector is increased, the reflector becomes less sensitive to variations of the light source, and hence this effect of a high intensity at the top of the beam becomes lessened as the focal length of the reflector increases. I have found, however, that it is possible to use a reflector having a longer focal length, and still get the high intensity at the top of the beam by providing a lens having certain prisms thereon isadapted to bend downwardly certain of the rays projected by the reflector to provide a beam of the desired light distribution.

' Another object of the invention is to provide a headlight having such a relation between the focal length of the reflector, the size of the filament, and the configuration of the lens, that a beam of substantially the same outline and cross-sectional intensity will be produced regardless of slight variations in the positioning of the'filament.

Another object of the. invention is to-provide a headlight adapted to project two beams of light, independently of each other, in which the relation between the focal lengt of the reflector, the distance between the filaments, and theconfiguration of thelens is such that I the angularity between the two beams will not vary substantially regardless of variation of the position of the filaments. One embodiment of the invention has been illustrated in the accompanying drawings, in which;

Fig. 1 is a sectional side elevation of a headlight embodying the invention;

Fig. 2 is a frontview of the lens shown in Flg. 1; j o

Fig. 3 is a sectional plan view of the lens taken on the line 33 of Fig. 2;

Fig. 4 is a sectional plan view of the lens taken of the line 4-4 of Fig. 2;

Figs. 5 and 6 are sectionalplan views of portions of the lens taken on the lines 55 and 6-6 respectively of Fig. 2;

Fig. 7 is a diagrammatical view of the projection of light rays from the headlight when the light source is at the focal point of the reflector;

Fig. 8 is a diagrammatical view of the light pattern projected upon a screen in front of the headlight;

Figs. 9 and 10 are diagrammatical views illustrating the direction of the rays pro ected by the headlight when the light source is above and below the focal point respectively;

Fig. 11 is a diagrammatical view showing the direction of the projected rays when the light source is in front of the focal point; and

Fig. 12 is a view similar to Fig. 11, but with the light source in back of the focal point.

Prior to my invention, the use of a relatlve- 1y short focal length reflector was almost universal, the focal length being 1 4 inches. The standard two-filament light bulb used in such a reflector consisted of two concentrated V shaped filaments having a base approximately 1/16" long spaced substantially equi-distant from the axis of the bulb, and approximately 9/64 of an inch apart. The manufacturing tolerancesfor these bulbs are plus or minus 3/64 for. transverse and axial positioning 'of the filaments and plus or minus 2/100 for the distance between filaments. By using this bulb in a short focal length reflector, the slightest variation of either of the filaments from their proper place adjacent the focal point of the reflector resulted in a distortion of the beam which in many cases would render the same unfit for adequate road illumination. B experimentation, I discovered that I coul increase the focal length of the reflector to approximately 1% inches, and by using a compensating lens still project thedesired beams at the same time rendering the reflector substantially insensitive to Variations of the position of the light source within limits considerably larger than the tolerances used in manufacturing. the light bulbs. In order to accomplish the desired objects of the invention, I have provided a reflector 10 having a relatively long focal length, and in which is mounted a socket 11 adapted to support a light bulb 12 by means of the usual bayonet slots 13, with the concentrated filaments 14 of the bulb adjacent the focal point 15 of the reflector. The filaments 14 are energized in the usual way, by means of a cable 16 connected to an external source of energy. The reflector 10 is suitably mounted in a casing 17 having a flange 18 to which the flange 19, forming the rim of the reflector, may be attached by means of the screws 20. A lens 21 is held against the flange 19 of the reflector and the connection therebetween sealed by means of the gasket 22. A rim 23 of conventional design holds the lens in place against the gasket and reflector. glass or other transparent material having a flange 24 slightly offset around its periphery for engagement with the gasket 22 on one side, and the rim 23 on the other, and divided into a plurality of prisms having slight inclination with respect to the vertical plane of the lens. Two of these, the upper prism 25, and the lower prism 26 extend completely across the lens, while the remaining two are positioned in the center of the lens and have the form of a trapezoid, the lower The lens 21 comprises a disk of Hi I prism 27 forming a base of the trapezoid,

and the upper prism 28 completing the upper portion of the trapezoid. At either side of the prisms 27 and 28, the glass is perfectly flat, forming two sections 29 and 30, through which light may project without any vertical refraction. The upper prism 25 starts preferably at the top in a plane with the flat portions 29 and 30 and extends downwardly downwardly at 'an inclination of approxiill;

mately 3, while the lower prism 26 also starts flush With the surfaces 29 and 30, and extends downwardly at an inclination of approximately 1 The base of the prism 27 was found to give good results when made approximately 3 4 inches wide, while the upper edge of the prism 28 was made approximately 1 inches wide. The side edges of these two prisms are preferably aligned with each other, as is clearly indicated in Fig. 2 of the drawing.

It will be evident to anyone skilled in the art that in any reflector, no matter which way the filament is moved with respect to the focal point, the light reflected by that part ations ofthe light source will be considerably increased in width. In the present invention, I have found by experiment that this insensitive surface may be a little wider than twice the focal length of the reflector, and, as illustrated in Fig. 2, represents the space between the bottom of the prism 25, and the top of the prism 26. The light reflected. through this part of the lens, therefore, will form an intense beam A (Fig. 8) and I have provided means to be hereinafter described, so that this beam will form the top of the main beam of light, which is projected down the road. In order to permit this beam to project far down the road, it is essential that the beam be fairly narrow in width, and, therefore, I have provided on the back .of this part of the lens, a series of flutes, each flute having a relatively long radius, so that although the beam is'spread, which is desirable toavoid shadows it is still kept within relatively narrow limits. t The attainment of the objects of the invention will be best understood by an examination of Figs. 7 and 8 of the drawings in which the projection of light has been illustrated with the light source at the focal point .of the reflector. Assuming a single light source 31 to be at the focal point a series of rays 6 are projected through the upper prism 25. As the light source is .at the focal point of the reflector, these light rays will be paralle]. until they strike the lens 21, whereupon the prism bends them down slightly. Another series} of rays -e .will be .projected" 7 through the prism 28 and, similarly to rays I), will be bent downwardly.

A third series of rays d will be projected through the prism 27, and will also be bent downwardl and a fourth. series of rays 0 will be projected through the prism 26 and be given a downward direction. It will thus be seen that all of the rays projected through prisms 25, 26, 27 and 28 are given. a downward direction, but inasmuch as these prisms have different inclinations, the rays will 'be projecteddownwardly at slightly different angles. Thus, the rays 6 areprojected downwardly silghtly, and will form a narrow horizontalpattern on a screen in front of the headlight corresponding approximately to the hori'zontal strip E shownin Fig. 8. I have found by experiment that in order to get the best results and produce a light pattern without holes therein that the risms should be inclined at the angles in icated above. With the prisms thus inclined, the prism 28 will throw the horizontal strip E ust underneath the intense part of the beam A projected through the sides 29 and 30 ofthelens. The

" prism 26 at the bottom will project agroup of rays 0 "which will form a thin, horizontal pattern C just below the pattern E, the prism- 25 at the top will project a group of rays 6 to form a pattern of light B below'the -pat-i.

tern C, and the prism 27 having the greatest;

inclination will throw a grou of rays d -on the screen to form a pattern at the lower end of the beam. The patterns. A, B, O,' D and E are only approximately shown inFig.

8, and it is to be understood that these patternslover-lap and blend with-one another,-

so that the general effect is a horizontal atch of light havinga considerablyahigher ulge at the center thereof, in'which the intensity of the light is the greatest. It is tobe noted that the chief object for placing the prisms in the lens, as .indicatedin the drawings, is to project all of the rays which will be substantially affected by variation of the light source below the intense part of the beam A. which is projected by the insensitive part of the reflector.

In Figs. 9 and 10, theefl'ect of raisin'gand lowering the filament .with respect to the focal point of the."reflectorhas beenfillustrated. In Fig. 9,-source 31 has been-shown above the focal point 15 ofthe reflector, and

the full lines indicate the inclination of .the rays of light with respect to parallel rays focal point. Inasmuch as the rays, pass through the same prisms, they are deflected downwardly, similarly as indicated in Fig.

3, but more so on account of the downward inclination of the rays given by the reflector.

(shown in dot and dash lines) which would I be projectedif the light source were at the The pattern of light, therefore, which is 1 formed by the rays projected, as in Fig. 9, is substantially the same as shown in Fig. 8, but at a slightly lower elevation. In Fig.

10 the rays are indicated as being inclined slightly upwardly, due to the placing of the light source 31 below the focal point 15, and

it is evident that inasmuch as the prismsrefract the light downwardly, the light pat- I tern-will be similar to that shown inFig. 8,

,. 11 and 12 show the result of placing I 12, wherein the rays are all shown as 'diver'g ing. In thisjcase, therefore, rays b and e diverge. from rays a and c, causing patterns B and E to move upwardly, and patterns C and D to move downwardly. It will thusbe evident that as the light source is moved with respect to the focal point of the refi'ector, the patterns B, C, D and E move with respect to each other, sometimes over-lapping more than at other times, but at no time'leav- -ing a space between any two/pf them, which would cause'a shadow in the beam, nor do they atany time rise above the intense part of the beam A.

It will be noted that the attern A. is lengthened slightly or shortene as the light source is moved behind and in front of the focal point of the reflector, but that it does not change vertically unless the light source is moved above or below the focal point. If a two filament lamp, therefore, is placed in the reflector with the filaments-one above the other, the beams projected independently by these two filaments will be substantially the same regardless of slight variations in the placing of the filaments with respect to the focal point, but one beam will be lower than the other beam depending on the relation between the focal length of the reflector and the distance apart of the filaments.

' It is evident from the above that I have provided a headlight which may be adapted to receive in fixed focus a headlight bulb, and which will not be affected by slight variations in the placing of the filament, due to manufacturing tolerances of the bulb, and which at the same time will produce a very desirable beam for driving purposes when one filament is energized, and another beam for driving in traffic declined below the eyes of an approaching driver when the other filament is energized. Y

My experiments have led me to believe that in order to have the angle between the beams not more than 3 degrees nor less than 2 degrees, the focal length of the reflector should not be more than fifteen nor less than ten'and one-half times the distance between the filaments.

In manufacturing lenses as described above I have found that if the angle of a prism is so great that it leaves a relatively great iorizontal distance at the bottom of the prism, the lens may warp due to the unequal cooling caused by the non-uniform distribution of glass or the lens may tend to stick to the l mold with the result that the inner side of the lens may be slightly concave and this deformation may be avolded by making two or more prisms in the place of the one. This will make no change in the direction of the rays projected as long as the prisrns have the same angle, but will merely decrease the thickness of the glass.

In this connection the angularity of the rays due to a given displacement of the filament which must be controlled by these prisms, is much less in the longer focal length than in the shorter focal length reflector thereby requiring less bending power and angle which means less thickness of glass in the prism and less prisms to accomplish the same result, wherefore the present invention considerablysimplifies the manufacture of lenses.

. The .lens described above and illustrated .n the drawings is adaptedTto give proper results when the filaments are spaced substantially equally one above and one below the axis of the reflector, but if it should be desired to place the bulb in such a position that one filament, for instance, would be substantially at focus and the other above the focus, the angles of the prisms would necessarily have to be slightly increased to accomplish the desired result.

By increasing the number of prisms without changing their angles also provides a means to change the appearance of the lens and .to add to this effect the flutes on the rear surface may be made wider or narrower, as desired, so that a large number of lenses may be made having the same light refracting properties but differing in appearance each from the other.

Theuse of a long focal length reflector produces 'a more compact beam of light with more even distribution of the intensity thereof over the entire light pattern and hence a more practical and desirable headlight for automobile use.

When a new bulb is inserted in the headlight, it may be found necessary to slightly tilt the headlightv casing in order to give the same inclination to the driving beam of each headlight, or, if desired, a small adjustment may be provided for this purpose. This adjustment, it is to be understood, will merely direct the beam, and is in no sense necessary to change the focus thereof.

Many modifications of the invention may be resorted to without departing from the spirit of the invention, and I do not desire to limit myself to the exact arrangement of parts shown in the accompanying drawings and described in the accompanying specification. Only in so far as I have particularly pointed out the invention in the accompanying claims is the same to be limited.

Having thus described my invention, what I claim is: l 1. In a headlight, the combination of a parallelizing reflector having a focal length of substantially 1 3/4 inches, a light bulb having two concentrated separately energizable filaments spaced apart substantially 1/8 to 9/ 64 of an inch located substantially in the focal plane of the reflector adjacent the focus; the focal length of the reflector being not less than 10 1/2 nor more than 15 times the distance apart of the filaments; said reflector being located principally to the rear of the focal plane but having its forward edge slightly in front of the focal plane, means to su port the bulb in fixed and non-adjustable re ation to the reflector; and a lens having transverse upper, central, and lower zones; the upper and lower zones and the middle portion only of the central zone having prisms thereon to deflect light downwardly; the construction of the headlight being such that the angle of depression between the top of the beams of light produced by the two filaments is not more than 3 degrees nor lessthan 2 degrees.

2. In a headlight, the combination of a parallelizing reflector having a focal length the distance apart of the filaments; said reflector having a reflecting portion located to the rear of the .focal plane and'having a forward portion extending in front of the focal plane, means to support the bulb in fixed and non-adjustable relation to the reflector, and means to deflect downwardly the rays issuing from the upper and lower zones and the middle portion only of the central zone of the re-- flector; the construction of the headlight being such that the angle of depression between the top of the beams of light produced by the two filaments is substantially not more than 3 degrees nor substantially less than 2 degrees.

3. In a headlight, the combination of a parallelizing reflector having a focal length of approximately 1 3/4 inches, a light bulb having two separately energizable filaments spaced apart substantially 1/8 to 9/64 of an inch located substantially in the focal plane of the reflector adjacent the focus; the focal length of the reflector being not less than '10 1/2 nor more than 15 times the distance apart of the filaments, said reflector having a primary reflecting portion located rearward- 1y of the focal plane and having an extension located forwardly of the focal plane, means to support the bulb in fixed and non-adjustable relation to'the reflector, and means to deflect downwardly the rays issuing from the upper and lower zones of the reflector; the construction of the headlight being such that the angle of depression between the top of the is substantially not more than 3 degrees nor substantially less than 2 degrees; a

. In testimon whereof, I affix my signature.

' S AMUEL F. ARBUOKLE.

CERTIFICATE OF CORRECTION.

Patent No. 1,826,712. Granted October 13, 1931, to

SAMUEL F. ARBUCKLE It is herebytcertified that error appears'in the printed specification of the above numbered patent requiring correction as follows: Page 1, line 63, for patent number "1, 662,938" read 1,622, 938; and that the said Letters Patent shouldvbe read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 15th day of December, A. D. 1931.

M. B. Moore,

(Seal) I Acting Gommissionerof Patents. v 

